Vacuum tube



Aug. 4, 1931.

J. V. CAPICOTTO VACUUM TUBE Filed June '10 Y 1924 INVENTOR J V QP/COTTO ATTORNEY Patented Aug. 4, 1931 UNITED STATES {PATENT-OFFICE JAMES V. CAPIGOTT'O, 0F BROOKLYN, NEW YORK, ASSIGNOR T0 DUBILIER CONDENSER CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

VACUUM TUBE Application filed June 10,

My invention relates to vacuum tubes, and especially vacuumtubes of thetype used in signaling by radio.

An object of my invention is to provide a vacuum tube equipped with novel means for preventing excessive electrical potentials or charges upon the grid, which is connected to the input circuit of the tube, With the result that I am enabled to dispense with the grid leak resistance usually employed, and the tube, further, becomes capable of better regulation than an ordinary adjustable grid leak will permit.

The nature of the invention will appear from the following description taken with the accompanying drawings, and the characteristics of the invention are precisely defined in the appended claims.

On the drawings,

Figure l'is an outlineof a circuit containing a vacuum tube according to my invention; and

Figure 2 is an outline of a similar circuit with a modification.

The same numerals identify the same parts throughout. r

In Figure 1, the numeral 1 indicates 'a coil which is in multiple with a condenser 2that may be adjustable. One terminal of this condenser and coil is joinedthrough a conductor 3 containing a small condenser of constant capacity 4, to the grid 5 of a vacuum tube T. Inside of this tube-T is also an ordinary filament 6, having terminals on the outside of the tube, and connected to the terminals of a small battery 7, through a rheostat indicated at 8. One pole of the battery 7 will be united by a conductor 9 to the other common terniinal of the coil 1 and condenser 2.

The tube T also contains a plate 10, the grid 5 being between this plate and the filament 6, and this plate 10 is joined through a pair of ear phones indicated diagrammati-' cally at 11, to a plate battery 12, which has one terminal also in circuit with the filament 6 in the usual fashion.

It is well-known that in the operation of tubes of this character, electrical oscillations coming from or through the oscillating cir-' cuit containing the coil 1 and condenser 2,

1924. Serial No. 713,118.

ary to employ an element having high electrical resistance between the coil 1 and condenser 2 and the grid 5; bridging this element across the terminals of the condenser 4. Such an element is known as grid leak resistance, and although it is of low conductivity, it sufiices to control the potential of the grid and keep the negative charge'thereon within limits, by enabling the electrons which are emitted from the filament 6 and which tend to accumulate on the grid 5, 5

to fiow away from the grid and along the conductor 3, and back to the filament 6by way of the conductor 9. In conjunction with my tube T, however, no grid leak resistance is necessary for I provide this tube with a sec- 7 0nd and smaller electrode element or filament 3 which is located inside the tube between the grid 5 and the first filament 6. One terminal of this filament is joined to the point of the grid which is connected to the conductor 3, or the lead-in terminal of the grid,

and the other terminal of the filament 13 is led out through the side of the tube to a potentiometer .14, which is joined to'one pole of a small battery 15, having its other pole connected to the conductor 3 between the tube and the condenser 4.

In practice, such a construction will-prevent the formation of excessive negative charges on the grid 5, while allowing the elec- 3'5 tron-s to return tothe filament 6 without being obliged to traverse the outside circuit and fiow back to the filament 6 by way of the conductor 9. The filament '13 constitutes primarily means for such a purpose, andits 96' temperature and potential is controlled by the battery 15 and potentiometer, orrheostat- 14. The filament 6 is positive with respect to the filament 13 and'the filament 13-serves in a; way, as a bridge between the grid 5 and filament 6, to allow the electrons which would otherwise accumulate on the grid 5, to flow directly back to the filament 6, without accumulating on the grid to such an extent'that the tube would cease to function. "At the 100 same time, the electronic emission between the filament 6 and plate 10 is allowed to take place in the usual manner. and the operation of the tube can be very advantageously con trolled by varying the resistance of the local circuit containing the auxiliary element 13. In fact, this second filament, through the action of the rheostat 14, really acts like a variable grid leak, tl e resistance of which can be very accurately adjusted. It is wellknown that all fixed and variable grid leaks now utilized are apt to change when used, so that the values of the resistance they offer become altered beyond the limits permitted by the tube; but my invention enables me to obtain all of the precise regulation which is needed and, at the same time, obviate the drawbacks which the ordinary varieties of grid leaks, and especially adjustable grid leaks now entail.

In Fi ure 2, the filament 13 is dispensed with and the battery 15 with the rheostat 14 outside the tube, are bridged across the two extremities of the grid inside the tube. This combination gives the same effect as before,

because through the battery 15 serving as means for securing the end desired, the grid 5 ma be heated so as to obviate excessive negative potentials the same as before. The numeral 16 indicates a wire connecting one terminal of the rheostat, to the inner end of the tube, while the battery 15 is joined to the terminal leading into the tube to the grid 5. Both these circuits shown in the drawings, the filament 13 of Figure 1 and the grid 5 without the extra filament shown in Figure 2,

must be so operated that the temperature of the filament 13 in the one case, and of the grid in the other, is maintained at the proper point, to secure the result aimed at and enable the electrons which tend to accumulate on the grid 5 to be removed and returned to the regular filament 6, without having to pass over the outside circuit, and hence no external J grid leak ever need be added.

My invention thus enables me to operate a vacuum tube with a high degree of efliciency and regulate it with precision; neither an external grid leak, or so-called grid bias battery ever being required.

It is to be understood that the foregoing description discloses only the best manner now known to me of putting my invention to practical use, but the right is reserved to make minor changes, particularly with regard to the arrangement of parts, and the substitution of equivalents, within the scope of the principle of the invention.

Having described my invention, what I believe to be new and desire to secure and protect by Letters Patent of the United States is 1. A vacuum tube comprising a grid, and means for enabling excessive negative charges tending to accumulate on said grid, to be re moved therefrom and conducted away by space discharge on the inside of the tube, said means comprising an element in the tube connected to the grid.

2. A vacuum tube comprising a grid and filament, a second filament in the tube between the grid and the first filament, and connected inside the tube with said grid, and a source of current supply connected to the second filament.

3. A vacuum tube comprising a grid and filament, a second filament in the tube between the grid and the first filament, and connected inside the tube with said grid, and a source of current supply connected to the second filament, together with a rheostat for controlling the said current supplied to the second filament.

4:. A vacuum tube, a plurality of electrodes within the tube, at least one of the electrodes being adapted to control electronic emission within the tube, and means for enabling excessive negative charges to be removed from said controlling electrode, the said means comprising an element capable of electronic emission within the tube and connected to said controlling electrode.

5. A vacuum tube having an anode, a cathode and a control electrode, and means comprising an electron emitting element within the tube and connected to the control electrode, and cooperating with said anode toremove excessive negative charges from the control electrode.

6. A vacuum tube having filament, plate and grid electrodes and means including an additional filament within the. tube, and connected to the grid for causing excessive negative charges tending to accumulate on the grid to be conducted away from the grid to prevent blocking of the tube.

7. A vacuum tube having filament, plate and grid electrodes, an additional filament within the tube for causing the removal of excessive negative charges tending to accumulate on the grid and thereby block the tube, a source of current supply for said additional filament, the filament being connected to one end only of said grid.

In testimony whereof I affix my signature.

JAMES V. CAPICOTTO. 

